1. Field of the Invention
This invention relates generally to machine tools of the type having tables which are rotatably indexed by geneva drive mechanisms, and is concerned in particular with an improvement in the positioning of the lock plates of such mechanisms in order to achieve optimum indexing accuracy.
2. Description of the Prior Art
Examples of known geneva drive mechanisms are disclosed in U.S. Pat. Nos. 1,975,008 (Kingsbury); 2,011,486 (Kingsbury); 2,021,030 (Swahnberg); 3,750,494 (Rice); and 4,918,826 (Moore et al).
In drive mechanisms of this type, and as is best illustrated for example in the Moore et al '826 patent, the lock plates are conventionally located on the underside of the rotatable table by locating pins or dowels. When setting up the machine to achieve accurate positioning of each work station at the desired angular location, the positions of the lock plates must often be readjusted with respect to the table. This in turn requires replacement of the existing dowels with substitutes that have been carefully machined to effect the required lock plate adjustment. This is a time consuming procedure, which may require several repetitions before finally achieving an acceptable degree of accuracy.
The objective of the present invention is to facilitate set up procedures by providing a means for more efficiently and readily adjusting the positions of the lock plates with respect to the table.